WO2004075977A2

WO2004075977A2 - Methods using diffuse field ultrasound-induced hyperthermia

Info

Publication number: WO2004075977A2
Application number: PCT/US2004/005955
Authority: WO
Inventors: C. Lawrence Christman
Original assignee: Christman C Lawrence
Priority date: 2003-02-27
Filing date: 2004-02-27
Publication date: 2004-09-10
Also published as: WO2004075977A3

Abstract

Uses for diffuse field ultrasound-induced hyperthermia are provided. The uses include treatment of cancer, especially lung cancer; improving acceptance of transplanted tissues and organs; and improving healing of wounds.

Description

METHODS USING DIFFUSE FIELD ULTRASOUND-INDUCED HYPERTHERMIA

Related Applications This application claims the priority of U.S. provisional patent application Serial No. 60/450,997, the disclosures of which are incorporated herein in their entirety. This application is also a continuation-in-part of PCT application no. PCT/US02/09035, the disclosures of which are incorporated herein by reference in their entirety.

Field of the Invention

The invention relates to methods and an apparatus for treating diseased tissue at least partly by temperature elevation and/or regulation. In particular, the invention relates to methods for treating diseased tissue and for transplanting tissue and/or organs, using ultrasound-induced hyperthermia. In such methods, ultrasound-induced hyperthermia can be delivered in conjunction with other forms of therapy that may be carried on simultaneously or sequentially, including radiation therapy and chemotherapy.

Background of the Invention

Ultrasonic waves are effective in providing therapeutic heating of tissue, which can be a useful technique in treating diseased tissue such as cancerous tissue. The use of therapeutic heating for treating diseased tissue relies on the effects of hyperthermia on tissue, which effects can be enhanced by the simultaneous or sequential application of radiation, among other ways.

Hyperthermia can be achieved by the application of energy in the form of, for example, microwaves, ultrasound waves, or radio-frequency waves. Hyperthermic toxicity, the direct killing of cells by overheating, is described in Overgaard, "The Current and Potential Role of Hyperthermia in Radiotherapy", Int. J. Radiation Oncology Biol. Phys., Vol. 16, pp. 535-549 (1989).

When hyperthermia and radiation are applied to tissue, an effect known as "hyperthermic radiosensitization" occurs. Radiation and hyperthermic treatment can be applied either simultaneously or sequentially.

It has now been discovered that ultrasound-induced hyperthermia can be advantageously used in conjunction with certain procedures, including surgical procedures, and can contribute to and/or enhance beneficial effects of such procedures. The present invention is directed to these and other important ends.

Summary of the Invention

One aspect of the invention is a method for treating diseased tissue in a mammal. The method includes inducing regional hyperthermia in the tissue by applying unfocused ultrasound waves to the tissue to achieve a diffuse area of heating. The heating can be regulated and can be applied within a therapeutic regimen. In some embodiments the method is used to treat a human patient. In some embodiments, the diseased tissue is lung tissue. In some preferred embodiments, the diseased tissue is cancerous tissue. In one embodiment of the invention, the method further includes applying to the tissue high-energy radiation, such as ionizing radiation, preferably concentrated on a treatment zone. In some preferred embodiments, the unfocused ultrasound waves are applied in conjunction with the high-energy radiation.

In another preferred embodiment of the invention, the method further includes administering to the mammal one or more chemotherapeutic agents in conjunction with the application of unfocused ultrasound and/or the application of high-energy radiation, either simultaneously or sequentially. The methods disclosed herein preferably use a particular device for providing ultrasound-generated hyperthermic treatment to a patient. The device includes a means for generating unfocused ultrasound waves; a means for obtaining temperature data from the tissue in situ; a central processing unit; an exposure tank; and a means for directing said ultrasound waves to said tissue.

A further aspect of the invention is an improved method for transplanting tissue from a donor to a recipient. The method includes inducing hyperthermia in the body of a donor such that the tissue to be transplanted reaches a temperature higher than the normal body temperature of the donor, maintaining the body of the donor at the higher temperature for a period of time, allowing the body of the donor to return substantially to normal body temperature, removing the tissue from the donor, and transplanting the organ into a recipient. In some embodiments, the tissue is part of an organ. In some embodiments, the tissue is an entire organ. In some embodiments, the tissue or organ is cooled following removal of the tissue or organ from the donor, for example, for storage prior to transplantation into the recipient. In some embodiments, the donor is a mammal, which can be a human or a non- human mammal. In some embodiments, the donor and recipient are human. A further aspect of the present invention is a method for treating a wound. The method includes using DFHT to increase the temperature of the wound.

These and other aspects of the present invention will be apparent to one skilled in the art in view of the following disclosure and the appended claims.

Brief Description of the Drawings

Figure 1 shows the positioning of a human patient in an exposure tank for treatment of the lung. Figure 2 is a schematic representation of the application of combining DFHT exposure with SFHT exposure for homogeneous tissue Figure 3 is a schematic representation of the application of combining DFHT exposure with SFHT exposure for tissues with different perfusion rates. Figure 4 shows a protective barrier formed behind the treated tissue, which protects sensitive tissue from over exposure.

Detailed Description of Preferred Embodiments

The present invention provides methods for treating mammals, which methods include the use of unfocused ultrasound waves to induce hyperthermia in a mammal.

The term "hyperthermia" as used herein to refer to the desired rise in temperature of tissue due to the application of energy such as ultrasound waves, means a therapeutically induced condition in which the temperature of the tissue is detectably higher than the normal range of body temperature in a healthy mammal. Normal ranges of body temperatures vary among different species of mammals and also may vary with the condition of the subject (e.g., by pathogenically induced fever) or the condition of localized tissue (e.g., by local inflammation). Generally, normal body temperature for a human is about 37 °C, although individual variations of plus or minus about 2 °C are not uncommon. For therapeutic uses, hyperthermia generally encompasses induced temperature in targeted tissue of a human of at least about 39 °C, preferably at least about 40 °C, more preferably at least about 41 °C, still more preferably at least about 42.5 °C. Even more preferably, for some applications, the induced temperature is about 43 °C. It is also preferable to permit a cool down time afterwards before removing the targeted tissue from the treatment apparatus. Thus, a patient is preferably allowed to rest in the treatment position following hyperthermic treatment for a few minutes. The methods and devices disclosed herein utilize diffuse ultrasonic waves. Ultrasonic waves can generally be classified as focused waves, plane waves, or diffuse waves. Diffuse ultrasound waves can be visualized as a superposition of a plurality of plane waves, which can have a variety of amplitudes, phases and/or propagation directions. "Diffuse ultrasound" comprises a continuum of diffuseness (from totally diffuse to less diffuse to nearly planar). One advantage of diffuse ulltrasound is substantial elimination of the importance of the position of transducers, the position of the target tissue, and the position of sensors used to measure decay rate. Other advantages of DFHT include the following: The method is simple to operate and is low-cost. DFHT is inherently safe because energy is deposited below the surface of the skin but not deeply into tissue. DFHT does not concentrate energy and is therefore not likely to produce focused tissue burns. By varying the center frequency of the exposure, the method allows control over depth of penetration.

SFHT is "scan focus hyperthermia". SFHT is disclosed in U.S. Patent No. 4,865,042 and U.S. Patent No. 4,549,533, the disclosures of which are hereby incorporated herein in their entirety. SFHT includes converging irradiating sound waves into an annular focal zone having a desired size. The method disclosed in the '042 patent uses a transducer and a plurality of elements divided at least in a circumferential direction of the face of the transducer so that the phases of drive signals may be changed according to the respective circumferential positions of the oscillating elements to rotate the phases of the drive signals n rotations in the circumferential direction. As a result, the annular focal zone of having a desired radius is formed, and integrated values of sound waves in the circumferential direction may be substantially zero on the focal plane so that an unnecessary secondary focal zone is prevented from being formed. An apparatus for use in SFHT is disclosed in the '533 patent. DFHT has a different acoustic absorption penetration profile compared to SFHT or conventional diathermy devices, which provides advantages when DFHT is used in combination with these other methods. DFHT allows the measurement of total energy absorbed during the exposure, which is useful for regulating the exposure. The method provides a relatively simple and cost effective way to expose large volumes of tissue. To change the volume of the tissue exposed requires a change to the size and location of the exposure, e.g., by changing the size and location of an exposure portal in a protective garment worn during exposure, but no other change to the apparatus.

The exposure field can be modeled because of the statistical nature of a diffuse field. At any point within the diffuse field over a sufficiently long period of time, the mean amplitude of all wave fronts is uniform and a wave has an equal probability of traveling in any direction. Moreover, the absorption of ultrasound waves by targeted tissue, which is a linear function of frequency for plane waves in mammalian soft tissue at the frequencies of interest, is not linear with diffuse ultrasound. Rather, for diffuse ultrasound, because the ultrasound energy approaches the target tissue from a plurality of angles, the absorption is approximately exponential near the tissue surface and becomes linear with deeper penetration. However, it will be recognized that in some applications, reduced diffuseness may be desired at the surface of the target tissue Additionally, the diffuseness of the ultrasound may be reduced as the ultrasound travels through tissue. Thus, while diffuseness of ultrasound is advantageous, the degree of diffuseness may be less than 100%.

The therapeutic application of diffuse ultrasound waves to tissue substantially without focusing to generate hyperthermia is referred herein to as "diffuse field ultrasound hyperthermia" or "DFHT". "Substantially without focusing" and "substantially unfocused" mean that no external device is used to create a focal point of ultrasound waves at a particular volume in targeted tissue. However, one skilled in the art will appreciate that some focusing of the ultrasound waves can occur as a result of properties of the tissue through which the ultrasound waves must pass in order to reach targeted tissue. A method and device that provide diffuse ultrasonic waves suitable for use in therapeutic applications are described in U.S. Patents No. 4,501,151 and 4,390,026, the disclosures of which are hereby incorporated herein by reference in their entirety. According to the disclosed method, a diffuse ultrasonic field is produced by frequency modulation of the ultrasonic waves by "white noise". As a result of variations introduced into the acoustic wavelength in this manner, the energy density applied is relatively smoothly distributed throughout the volume of the field, and not concentrated at peaks or absent at nulls that otherwise would be produced by standing waves. "Radiation", as used herein to refer to therapeutic energy applied in conjunction with ultrasound, includes all ionizing radiation having energies from about 125 KeV to about 45 MeV, preferably from about 4 MeV to about 23 MeV, more preferably about 8 MeV. Preferred ionizing radiation is photon radiation or electron beam radiation. "In conjunction with", as used herein to refer to the combined use of ultrasound-generated hyperthermia and radiation therapy, includes the application of ultrasound simultaneously with radiation, as well as the application of ultrasound sequentially with radiation. "In conjunction with", as used herein to refer to the combined use of ultrasound-generated hyperthermia and chemotherapy, includes the administration of chemotherapy prior to, during, and/or following the application of ultrasound. "Simultaneously", as used herein to refer to the application of ultrasound and radiation to diseased tissue, means that both ultrasound waves and radiation are applied concurrently for at least some period of time. Preferably, when used simultaneously, ultrasound waves and radiation are applied concurrently for at least about five minutes, more preferably at least about ten minutes, still more preferably for at least about twenty minutes, and even more preferably for at least about 30 minutes. In some embodiments, ultrasound waves and radiation can be applied simultaneously for about forty- five minutes. The practical upper limit of the time of exposure of a patient to ultrasound and/or radiation is determined in substantial part by tolerance on the part of the patient. Simultaneous application of ultrasound waves and radiation is not intended to preclude the application of ultrasound waves or radiation alone for a period of time in addition to the concurrent application thereof. Thus, for example, a treatment modality can include the initial application of radiation alone, followed by the application of ultrasound waves and radiation concurrently, followed by the application of radiation alone. Such alternating treatment may be carried out in any order.

"Sequentially", as used herein to refer to the alternate application of radiation and ultrasound, means that radiation and ultrasound can be administered in any order and with or without intervening gaps of time, wherein either radiation or ultrasound is applied alone during at least one phase of treatment. The order of application of radiation and ultrasound in sequential application thereof is not believed to be critical. For some applications, the sequential application of radiation and ultrasound may have certain advantages in comparison to the use of both forms simultaneously. Optionally, there may be a delay following one or more, or each, application of ultrasound waves and/or each application of radiation. A suitable delay period may be, for example, three, four, or five days. The determination of the appropriate delay time between sequential treatments is within the purview of the skilled clinician.

"Patient", as used herein, refers to an animal to whom treatment, including the application of ultrasound, is administered. Generally, a patient is a mammal, and can be a human or non-human mammal. In one aspect, the invention provides methods and devices for the treatment of diseased tissue, in particular cancerous tissue, by the application of ultrasonic waves to the tissue to generate hyperthermia in the tissue. It has now been discovered that the application of ultrasound waves to generate hyperthermia throughout targeted, diseased tissue and surrounding tissue, substantially without focusing the ultrasound waves, improves the effectiveness of hyperthermia in treating diseased tissue. The improved effectiveness has been observed in the treatment of cancer tumors, and is enhanced when hyperthermia is used in conjunction with radiation and/or chemotherapy. It has further been found that the combination of chemotherapy and ultrasound-induced hyperthermia is more effective in treatment of cancerous tumors than chemotherapy alone or ultrasound-induced hyperthermia alone. It is not intended that the present invention be bound by any particular theory. However, in connection with the administration of chemotherapeutic agents in conjunction with ultrasound, it is believed that hyperthermia generates localized increased perfusion in targeted and surrounding tissue, which improves the delivery of chemotherapy agents to targeted tissue such as tumors. It is also believed that hyperthermia and ultrasound can change the transport characteristics of cell membranes.

The desired cytotoxic effect of heat treatment on targeted cells is optimally achieved before the stage at which angiogenesis occurs. Angiogenesis, the development of new blood vessels, is necessary to maintain homeostasis (normal levels of oxygen and nutrients) with growth of a tumor. The tumor cells can become hypoxic if the tumor has outgrown its blood supply. Hyperthermia is particularly effective for treating hypoxic cells, while other treatment modalities including ionizing radiation may fail. Since the production of free radicals is less likely in hypoxic cells than in well- oxygenated cells, and free radicals are produced when radiation interacts with water in the presence of dissolved oxygen atoms, hypoxic cells are particularly resistant to injury from radiation. Because blood flow is restricted in hypoxic cells, such cells can also be resistant to chemotherapy, since they are likely to receive a lower local or internal dose of chemotherapeutic agent. Notwithstanding the foregoing, it is understood that certain cytotoxic mechanisms including those discussed hereinabove may be involved in the effectiveness of the methods disclosed herein in treating cancer and particularly microtumors, which are present long before angiogenesis occurs. While it is not intended that the invention be bound by any particular theory, it is believed that heating tissue for an extended time causes stress to the cells and elicits a biochemical stress response that involves the production of a set of proteins collectively called heat shock proteins (HSPs). In some embodiments, the methods and devices disclosed herein use hyperthermia delivered using DFHT alone to elevate and hold the temperature within tissue or an organ to be transplanted in the hyperthermia range for sufficient time to elicit the HSP response. In other embodiments, the methods and devices disclosed herein use hyperthermia in conjunction with other treatments, such as chemotherapy and/or radiation therapy, to treat diseased tissue. The methods and devices disclosed herein are useful in treating diseased tissue. Diseased tissue includes, in particular, cancerous tissue and more particularly tumors. More particularly, the methods and devices herein are useful in treating cancerous tumors in non-bony tissue, such as the breast, lungs, brain, prostate, testicles, kidney, liver or uterus. Generally, the methods and devices disclosed herein are advantageously used for treatment of cancer in tissues where acoustic impedance differences in targeted and surrounding tissue are minimal. The acoustic impedance for soft, i.e., non-bony, tissue and that of body fluids are similar, and the methods and devices disclosed herein are suitable for use in such soft tissue. In contrast, the presence of bone and/or gas-filled cavities adjacent to soft tissue may reduce the effectiveness of DFHT due in part to the reflection of ultrasound waves. In highly preferred embodiments, the methods and devices disclosed herein are used to treat lung cancer. DFHT can be used as a replacement for radiotherapy or in conjunction with radiotherapy, alone or in conjunction with radiotherapy in combination with chemotherapy. Chemotherapeutic agents can be administered to a patient while the patient is positioned for ultrasound therapy. A drug, such as an anti-cancer agent, can be injected into the bloodstream and, concurrently or alternately with the injection, ultrasound is applied through water to a patient immersed in the water in a tank. Anti-cancer drugs for use in chemotherapy are known to those skilled in the art. Examples of anti-cancer drugs useful in treating lung cancer include: Gemzar® gemcitabine, Taxotere® docetacel, Taxol® paclitaxel, Navelbine® vinorelbine, Camptosar® irinotecan, and cisplatin.

DFHT allows exposure of larger portions of a patient's body, and in particular enables a clinician to treat an entire organ, such as the lung, in contrast with the direct exposure of substantially only the targeted tissue, e.g., tumor, which can be accomplished using conventional, focused ultrasound. For the inducement of hyperthermia by DFHT, for a variety of therapeutic applications including treatment of disease, e.g., cancer treatment, tissue or organ transplantation, or wound healing, a patient to whom DFHT is to be administered is substantially, preferably fully, immersed in a tank of water. Typically, the temperature of the water in the exposure tank is maintained below normal body temperature and is controlled and adjusted to cool the surface of the skin in contact with the water in the exposure tank. This cooling helps to move the maximum tissue temperature deeper into the tissue of the patient. Another way of controlling the depth of penetration of heat is by adjusting the center frequency of the ultrasound DFHT exposure. Higher frequencies (5.0 MHz to 2.0 MHz) produce more peripheral heating; lower frequencies (2.0 MHz to 0.5 MHz) produce deeper heating.

For example, for treatment of lung cancer, the patient is preferably immersed up to the neck, as shown in Figure 1. Preferably, the patient wears a protective suit (not shown) that can provide an air barrier between the water 21 in the tank 22 and any tissue not intended to be treated and protect critical tissue sites. The suit has an opening, called a treatment portal, which allows water within the exposure tank to contact with the tissue to be treated. The portal can include a means to seal the skin around the portal from leakage. Suitable adhesives that are biocompatible and resistant to water are available. It is highly preferred that the suit protects the spine from being heated.

For example, for treating a patent with lung tumors confined to the right inferior lobe, the portal allows water in the exposure tank to contact the skin in proximity to the location of the tumors or the inferior lobe. The suit protects other areas of the body that are not being treated and are submersed within the exposure tank from ultrasound heating. Other portal configurations can be designed to treat other treatment sites. The suit can be made of, for example, low cost plastic film or sheet and have a construction similar to that of a space suit or a scuba suit with appropriate weights strapped to the patient to prevent flotation. For example, weights can be attached by using attachments similar to those used by athletes to attach protective gear. Hook-and-loop type attachments are exemplary fasteners that are reusable and/or disposable and relatively low cost. Other methods and devices for shielding areas not to be treated, and for attaching weights to a patient, can be readily selected by one skilled in the art. Preferably, the suit contributes minimal or no acoustic loss at the ultrasound frequencies used for the DFHT. Also preferably, the suit has an opening to expose the tissue of the patient where treatment is needed. For some applications, it may be desirable that the suit is of relatively low cost and is reusable and/or disposable.

With ultrasound, any interface between two different tissues where there is a change in density creates acoustic reflections and can lead to excess heating at the interface. The junction between muscle and bone is an example of where excess heating can occur due to ultrasound propagation. In treating lung cancer, it is highly preferred that the skin above each rib be protected from exposure to the DFHT. A strip similar to an adhesive bandage strip is useful for this purpose. The inside layer of the strip has an adhesive to stick to the skin. The interior of the strip contains an air pocket, which reflects any ultrasound back into the exposure tank.

It will be recognized by one skilled in the art that ultrasound is advantageously applied to tissue for a time sufficient for the tissue to reach therapeutic temperature, i.e. to achieve hyperthermia, which can take about 10 or 15 minutes or more. Preferably, the tissue is maintained at therapeutic temperature for at least about 10 minutes, more preferably at least about 20 minutes and more preferably at least about 30 minutes. Also preferably, the tissue is maintained at therapeutic temperature for about 90 minutes or less. The upper limit is not critical; however, generally the relative increase in therapeutic effectiveness with time declines after about one hour of treatment. Typically, the tissue is maintained at therapeutic temperature for about 45 to 60 minutes. Generally, relatively higher temperatures can be endured by tissues for relatively shorter times, and a modest temperature elevation can have a substantial effect if sustained over time.

Also preferably, induced body temperature in targeted tissue of a human undergoing hyperthermic therapy does not exceed about 48 °C. More preferably, such induced temperature does not exceed about 47 °C, and even more preferably, such induced temperature does not exceed about 46 °C. It is highly preferred that induced temperature of targeted tissue during hyperthermic therapy is maintained at about 44 °C ±2°C. When the temperature of targeted tissue is within the preferred range, there may be local hot and/or cool spots; i.e., local areas having temperatures as low as about 40°C and as high as about 50°C. It is preferred that such hot and cool spots be minimized. In particular, cool spots can reduce the effectiveness of hyperthermic treatment. In comparison with focused ultrasound, the use of diffuse ultrasound reduces the occurrence of cool spots. Thus, in highly preferred embodiments for both cancer treatment and transplantation, the target tissue is maintained at a temperature of about 43 °C for about 20-60 minutes.

Specific times and temperatures for delivery of diffuse ultrasound to induce hyperthermia depend in part on the purpose for the hyperthermic treatment and the characteristics of the patient being treated. One method for expressing the relationship between temperature and time, useful for quantifying hyperthermic exposure, is "equivalent minutes at 43 °C", which is disclosed by Sapareto et al., Int. J. Radiation Oncology, Biology, Physics 10(6), pp 787-800 (1984), the disclosures of which are hereby incorporated herein by reference in their entirety. Using the disclosed method, an estimate of the equivalent treatment time at a particular reference temperature, e.g., 43 °C can be determined from the actual temperature during treatment as a function of time, based on a mathematical conversion discussed by Spareto et al. Moreover, Leopold et al., have disclosed in Int. J. Radiation Oncology, Biology. Physics 25(5), pp 841-847, the disclosures of which are hereby incorporated herein by reference in their entirety, that the cumulative time at a given temperature can be used to predict therapeutic benefits from a particular hyperthermic treatment. Using such a model, treatment can be stopped when the target tissue has been administered treatment equivalent to 20-60 minutes at about 43 °C. In some embodiments, DFHT ultrasound can be used in conjunction with whole-body hyperthermia, also referred to as "systemic hyperthermia". With whole-body hyperthermia, substantially the entire body of a patient is maintained at therapeutic temperature, which reduces the effects of phenomena such as perfusion that can reduce local body temperature at targeted tissue and lower the effectiveness of hyperthermic treatment. Whole-body hyperthermia means that a patient's core body temperature is on average at least about 2 °C above the patient's normal body temperature.

When DFHT is combined with whole-body hyperthermia, the protective suit preferably has a provision to reduce heat loss through the skin over which it covers. This can be accomplished using insulation, heating, increasing the humidity, circulating the air within the suit or any combination thereof. A hood, which covers the patient's head, can be used to increase the temperature and humidity of air the patient breathes. The patient's vital signs including core body temperature are monitored during treatment.

It has been discovered that the use of DFHT can provide advantages in the use of hyperthermia for the treatment of lung cancer. Because ultrasound will not penetrate through air, prior to treatment, a body cavity surrounding a body part to be treated, or in the case of lung treatment, the lung itself, is generally filled with a suitable liquid. The liquid can be, for example a liquid perfluorochemical, liquid saline or other suitable liquid. The advantage of using a perfluorochemical is that the liquid traps oxygen and carbon dioxide and can be used to ventilate the lung during treatment. The disadvantages of using perfluorochemicals are that they are expensive and their acoustic absorption is high relative to saline, which can make it difficult for ultrasound to penetrate deep into the tissue.

Using liquid ventilation provides two different methods for heating the tissue: heating the liquid, and heating the lung using ultrasound. Liquid ventilation can be directed to both lungs, a single lung, a single lobe or a partial lobe. The right human lung has three lobes and the left human lung has two lobes. For treatment of a single lobe or partial lobe, the need to oxygenate the liquid becomes less important and the use of saline or other non-oxygenating liquids can be more favorable. Particularly when used in conjunction with liquid ventilation, DFHT provides advantages over traditional ultrasonic therapy, because with DFHT, the degree of heating is independent of the location of the patient within the treatment tank.

In one method, a combination of ultrasound hyperthermia methods and overlapping fields are used to construct three dimensional treatment volumes. An application of this method is considerably different from its application using ionizing radiation. This method can be equally useful for lung cancer treatment and accelerated wound healing applications. It has been found that the inducement of hyperthermia in a wound can aid and/or accelerate healing of the wound. For radiation therapy, it is common practice to plan a treatment session or a series of treatment sessions so that a nearly uniform treatment dose is achieved. In the case of ionizing radiation, the dose is cumulative over the lifetime of the patient. Therapeutic doses of radiation once in a lifetime preclude treating the same tissue with radiation later in life. Standard practice is to use a large number of dose fractions over the course of six weeks so that the sum total of accumulated dose achieves some therapeutic total value. For example, in breast cancer, the patient receives weekday dose fractions of about 2.0 Gy for five weeks for 25 treatments and a total dose of 50 Gy. To compute the total dose, investigators sum the individual contribution of dose over time and over tissue volume. Two exposures side by side are biologically equivalent to one exposure over the same volume, which gives the same total dose. The time separation of exposures is not critical. For overlapping exposures the technician must be careful so that tissue within the overlapping regions is not overexposed. While multiple exposures with time and space are useful for achieving therapeutic benefit for hyperthermia and specifically for ultrasound hyperthermia, the rules for combining individual treatments are different. These differences have important clinical application. The rules depend on the time frame considered. The rules fall into three categories: short, intermediate and long. The time intervals presented are for human tissue; the time intervals for other mammals may differ but can be derived by a person skilled in the art, from the values given below, using a scaling factor.

For combining multiple short-term exposures, where short term means less than six hours, equivalent minutes at 43 °C are used. First the time, temperature and spatial profile for the treatment are measured or predicted. These profiles are converted into the time at a standard and constant temperature using the approach of Sapareto et al. Typically, the actual time temperature profile is converted into equivalent minutes at 43 °C, which quantity is called the "thermal dose". For the ranges recited herein, within the short-term time frame, thermal dose is additive for multiple exposures until it reaches saturation. The saturation value can be dependent on the specific tissue but is generally in the range of from 20 to 60 equivalent minutes at 43 °C. Exposures that provide a thermal dose greater than 60 equivalent minutes at 43 °C produce little difference in biological effect. It is preferred not to exceed the threshold for permanent thermal injury, which is generally greater than 60 equivalent minutes at 43 °C.

For combining multiple exposures that span the long-term time frame where long term is greater than six days, the rule is that exposures are independent. Thus, if the patient receives a thermal dose of 45 minutes at 43 °C on day one and they receive a thermal dose of 45 minutes at 43 °C on or after day seven to the same tissue, their cumulative thermal dose on day seven is 45 minutes at 43 °C. This combination rule is in sharp contrast to the case for ionizing radiation where the total dose accumulates over a patient's lifetime and never resets to zero.

For combining multiple exposures that span the intermediate time frame, which ranges from 6 hours to 6 days, the combination rule is complex. One clinically useful case occurs when the treated tissue achieves thermal tolerance. Thermal tolerance occurs when tissue is stressed with hyperthermia and allowed to recover. When the same tissue is stressed again within the thermal tolerance window, the tissue is highly resistant to thermal injury. The thermal tolerance window extends from six hours after the end of the initial stress to six days after the initial stress. The protective properties of the initial stress reach a maximum after six hours and slowly decay until the tissue returns to baseline after six days. In some applications, subsequent hyperthermic treatment can be administered to a patient in tissue which has acquired thermal tolerance. Such subsequent hyperthermic treatment can be administered SFHT or DFHT.

An aspect of the invention is the use of DFHT to pretreat tissue or organs prior to removal of same from a donor and transplantation into a recipient. It has now been discovered that pretreatment with DFHT of organs to be transplanted, by inducing hyperthermia in a donor of an organ, can improve the success of transplantation. (Pretreatment may also be referred to as preconditioning).

Prior methods for inducing hyperthermia for therapeutic purposes relied on whole-body hyperthermia. In order to reach and maintain therapeutic hyperthermic temperatures, such procedures required treatment for a time that could render the treatment risky for the patient. An emergency team for cardiac resuscitation would likely be required, in case the patient would go into cardiac arrest. Thus, DFHT provides an advantage in that it is more tolerable and safer for a patient than whole body hyperthermia. Even if whole body hyperthermia is used in conjunction with DFHT, e.g., as an auxiliary treatment, the time and temperature of treatment of the whole body could be significantly reduced if DFHT is used to target tissue to be treated. Pretreatment of tissue using conventional techniques to induce hyperthermia is disclosed, for example, in Terajima et al., Shock, vol. 12, no. 5, pp 329- 334 (1999)(liver); Hiratsuka et al., J. Heart Lung Transpl. 17(12), pp 1238-46 (1998) (lung); Perdrizet et al., Current Surgery January-February 1989, pp 23-26 (kidney); and Stojadinovic et al., Gastroenterology 109, pp 505-515 (1995) (intestines).

In an exemplary process of transplanting tissue or an organ from a donor mammal to a recipient mammal, e.g., a human, the donor is subjected to hyperthermia for up to one hour. The body temperature of the mammal is allowed to return to normal and the mammal is unstressed during the recovery period, which can last from 4 to 24 hours or longer. After sufficient time has passed to produce injury from the loss of oxygen to the tissue, the tissue is reperfused, i.e., blood circulation is allowed to return to the tissue. When pretreated mammals are compared to non-pretreated mammals, the pretreated mammals show less injury due to reperfusion.

The inducement of hyperthermia by DFHT for pretreatment of organs for transplanting can be used in conjunction with the transplantation of a variety of tissue and organs, including lung, liver, kidney, colon and rectum and the tissue thereof. In addition, the methods disclosed herein can be used in conjunction with both human transplantation (wherein tissue or an organ comes from a human donor and is transplanted into a human recipient) and xenographic transplantation (wherein tissue or an organ comes from a non- human donor, such as, for example, a pig, and is transplanted into a human recipient).

Organ transplantation is a stressful medical procedure. The tissue or organ to be transplanted is surgically isolated and removed. If the tissue or organ is not to be immediately transplanted into a recipient, the tissue or organ can be stored using standard procedures that involve submersion in various isotonic solutions and cooling, then surgically placed into the body of the recipient. Cooling is used to lower tissue metabolism and preserve the organ for transportation to the recipient. Prior to transplantation, the cooled tissue or organ is warmed and connected to the recipient's circulatory vessels. The final stage in transplantation is reperfusion of the tissue or organ with blood supply from the recipient. It is believed that pretreatment of tissue or an organ to induce hyperthermia prior to transplantation will render the organ, once transplanted, more resistant to reperfusion injury, leading to a lower rejection rate for treated transplanted tissue and organs compared to non-treated organs. Pretreated tissue and organs can survive longer in cold storage prior to successful transplantation.

The process of ischemia/reperfusion is particularly damaging to the healthy transplanted organ. During ischemia the organ's normal blood supply is removed, which produces hypoxia. During reperfusion, oxygen from the reconnected blood supply enters the cells, producing free radicals, which destroy cellular structures. Ischemia/reperfusion injury limits the storage time for transplanted organs and can lead to transplantation failure. Different organs have different sensitivities to reperfusion injury. Pulmonary tissue and the mucosa of the intestine are particular sensitive to reperfusion injury. It is believed that inducing hyperthermia, and specifically using DFHT, to pretreat the organ reduces the occurrence and degree subsequent reperfusion injury.

To prevent subsequent injury to tissue or to an organ, it is desirable that the degree of hyperthermia induced be high enough and that the induction of hyperthermia be maintained for long enough to induce the production of HSPs, although the invention is not intended to be bound by any theory related to HSPs. Generally, as discussed hereinabove, maintaining the tissue or organ at a temperature of at least about 43 °C for at least about 20 minutes is preferred, preferably from about 20 minutes to about 60 minutes. It is also preferred that transplantation of the tissue or organ not be carried out until a sufficient delay has passed during which the desired protection can be achieved by, for example, the generation of heat shock proteins. Generally, a delay of at least about four hours is desirable between the end of the hyperthermic treatment and the initiation of the surgical procedure for transplantation, which, is intended here in to mean the time at which the donor blood supply to the tissue is stopped prior to its removal. Preferably, the delay is about 48 hours or less, more preferably about 24 hours or less, and even more preferably about 12 hours or less. Generally, after a delay of about five days, the cells in the tissue or organ can be expected to have returned to their normal prestressed state and thus any therapeutic advantages due to the hyperthermia can be lost.

One problem that can be encountered when trying to heat a whole organ is the need to protect tissue behind the organ from unneeded and potential damaging thermal exposure. As illustrated in Figure 4 and Figure 4a, a protective barrier can be placed behind the organ using the following process. This process involves minimially invasive endoscopic surgery to inject a gel matrix 10 behind the organ 11 , which both protects tissue behind the matrix and reflects energy back into the organ to heat the most proximal region of the organ. Although this process is exemplified with respect to the transplantation of an organ, the process is useful for treating diseased tissue with hyperthermia, particularly cancerous tumors, as well as for using hyperthermia to treat internal wounds such as internal surgical repairs.

The endoscope includes one or more of the following features: a tip, a means to illuminate tissue in front of the tip, a means to display images of tissue near the tip, a means of bending the tip to change its direction of travel and thus steer the endoscope, a means for injecting a viscous liquid, and a means for injecting compressed air. Endoscopes having some or all of these features are commercially available or suitable endoscopes can be modified from commercially available endoscopes.

The surgeon makes a small incision in the skin of the patient, and inserts the endoscope. Using light projected to the tip and the image protected back from the tip of the endoscope and the ability to steer the tip of the endoscope, the surgeon directs the endoscope through tissue spaces, exercising care to avoid puncturing organs or rupturing major blood vessels.

In some cases, a brief blast of compressed air delivered from the tip of the endoscope can be used to temporarily inflate the space between adjacent tissue, creating a path for the surgeon to follow. Using a combination of methods, the surgeon positions the tip of the endoscope behind the distal end of the organ to be transplanted. Once positioned, the surgeon injects a viscous liquid, the properties of which are discussed hereinbelow, through the endoscope into the tissue space behind the organ. By controlling the injection rate and the retraction of the tip of the endoscope, and by repositioning the endoscope and repeating the steps above, the surgeon deposits a bolus of the viscous liquid behind the organ. This process causes minimal trauma to the patient and has low morbidity and few complications requiring medical intervention. The bolus becomes a barrier that reflects ultrasound that propagates through the organ.

The viscous liquid that is injected preferably has certain properties that make it suitable for use in this process. During the initial injection, the liquid flows easily through the endoscope. Once in contact with the tissue, the liquid forms a dense, flexible and biocompatible matrix. Within about one to two weeks, the matrix dissolves and is resorbed. Many suitable liquids are available, including polysaccharide solutions, gel compounds such as agar agar. A combination of liquids can be used. During the injection process, acoustic scatterers are suspended into the liquid so they become dissipated in the matrix that forms behind the organ. The scatterers can be of two general types: they can be filed with materials whose acoustic impedance is lower than water; or they can filled with materials whose acoustic impedance is higher than water. Liposomes filled with air are an example of the former; glass microspheres are an example of the latter. The purpose of the matrix is to suspend acoustic scatterers uniformly behind the organ. The purpose of the scatterers is two-fold. First, the scatterers prevent acoustic energy from propagating behind the barrier and thus protect critical tissue like the spine from over exposure. Second, the scatterers redirect energy back into the organ and heat the distal side of the organ.

Ideal scatterers have the following properties: They are small and can be easily injected through the endoscope. They have an acoustic resonance near the center frequency of the ultrasound exposure field. They are biocompatible and are stable within the matrix material. After a reasonable time, such as, for example, two weeks, they dissolve and are resorbed and removed from the body through natural physiological processes. Air-filled liposomes (Figure 4, 12) are ideal scatterers; for example, air-filled liposomes near 0.3 urn in diameter are resonant at an acoustic frequency of approximately 1.0 MHz, which means have a local maximum scattering cross section at that frequency.

One exemplary embodiment of a method for using DFHT to improve the success of tissue or organ transplantation can be carried out as follows, as shown in Figure 2. This embodiment illustrates a hyperthermia treatment intended to precondition an organ 30, in this case part of the liver, prior to transplantation. For this example, multiple exposures are used and multiple ultrasound hyperthermia methods. The donor of an organ or tissue is subjected to hyperthermia using DFHT. The donor preferably wears a protective suit 31 , as described hereinabove, with an open portal 32 to allow exposure of the organ or tissue to be transplanted to ultrasound within the tank. The suit protects other body tissue from exposure to the ultrasound. In a typical application, ultrasound is delivered for about 20 to 60 minutes. Preferably, the tissue reaches a temperature from about 42 °C to about 45 °C. Desirably, the temperature within the tissue or organ reaches about 43 °C. The patient is preferably subjected to DFHT significantly long to achieve a thermal stress that elicits a strong HSP response within region A (33). In a specific embodiment, DFHT can be delivered to provide thermal doses in the range of between 20 to 60 equivalent minutes at 43 °C, wherein "equivalent minutes" have the meaning disclosed hereinabove, which dose is sufficient to achieve this response. In Figure 2, the tissue behind region A does not achieve a sufficient dose. In some preferred embodiments, the temperature is maintained for about 20 to 60 minutes.

At the end of the exposure, the treated tissue rapidly (within 2-3 minutes) returns to normal body temperature. After the exposure, the patient is removed from the tank and allowed to rest. After a suitable delay, for example between 6 and 12 hours, the patient receives a second hyperthermia treatment, this time using ultrasound SFHT. As shown in the illustration, the exposure this time extends deeper into the tissue. The area labeled region B (34) achieves a thermal dose sufficient to elicit a HSP response in region B. If the SFHT treatment was given without a treatment intended to preconditioning the tissue, part of the intersection of regions A and B (35) could have sustained thermal injury. Due to the prior DFHT treatment and subsequent delay, the preconditioned tissue in region A has achieved thermal tolerance and is highly resistant to further heat stress. In this way, multiple exposures can be given that, by preconditioning and subsequent exposure of the tissue, build up regions of tissue that achieve a thermal dose sufficient for the desired therapeutic benefit.

There is no limit to the number of preconditioning exposures and subsequent deep treatments with the following exceptions. It is highly desirable that the delay between each preconditioning treatment and subsequent treatment is at least six hours. The total treatment plan is preferably completed before thermal tolerance has returned to baseline, which typically happens within six days. In standard clinical practice, the total treatment plan is generally completed within 72 hours. Because of differences in depth of penetration and coverage volume, DFHT is usually administered first followed by other DFHT treatments or followed by multiple SFHT treatments.

In the foregoing example, the tissue of interest is relatively homogenous and uniformly perfused.

Another example includes using the protective properties of preconditioning when applying multiple hyperthermia exposures. This example is illustrated in Figure 3. The tissue is not uniformly perfused. The exterior 41 of the organ has normal pefusion while the center (medullary region) 42 of the organ is highly perfused. Such differences in perfusion are common in some organs, including kidney, liver, and lung. As shown in Figure 3, the initial DFHT exposure produces thermal tolerance in the lumen 43 of the organ. The relatively higher perfusion within the center of the organ reduces the temperature therein, and can preclude adequate treatment of the region where the temperature is insufficiently high. After a suitable delay, e.g., about to 12 hours, the patient receives a SFHT treatment concentrated within the medullary (interior) region of the organ. During the second treatment, a therapeutic dose is delivered to the cortex but the normally perfused tissue surrounded the cortex is protected from thermal injury due to thermal tolerance.

In typical treatement processes, after hyperthermia treatment, the patient is removed from the treatment water and the body temperature is allowed to return to the patient's normal body temperature. In a typical application, the patient rests for between 4 and 12 hours, e.g., about 6 hours. In some applications, the patient rests for between 12 and 24 hours. After the rest period, surgery to remove the tissue or organ is performed, and the tissue or organ can be immediately transferred to a recipient, or stored and cooled using known methods. After the tissue or organ is transported to the recipient and the recipient is surgically prepared, the tissue or organ is transplanted into the recipient. Compared to non-pretreated controls, organs pretreated using hyperthermia induced with DFHT have less reperfusion injury after transplantation.

In preferred embodiments for delivery of DFHT for treatment of disease or pre-treatment of tissue or organ prior to transplantation, ultrasound waves of two or more different frequencies are applied to tissue. The lower the frequency of the ultrasound waves, the more deeply into tissue the ultrasound waves penetrate. Conversely, the higher the frequency of the ultrasound waves, the less deeply into the tissue the ultrasound waves penetrate, and certain lower frequency ultrasound waves do not penetrate substantially beneath the surface of tissue to which the ultrasound waves are applied. If the targeted tissue is immersed in a fluid, higher frequency waves may be substantially absorbed by tissue located at or near the interface between the tissue and the fluid. By controlling the frequency or frequencies of ultrasound waves, a clinician applying the ultrasound waves to tissue to generate hyperthermia can control the temperature and temperature distribution of the tissue. It is thus possible to generate desired temperature profiles throughout the tissue. In some embodiments, it is preferred to generate substantially uniform temperature profiles. By "substantially uniform temperature profiles" is meant a variation in temperature of less than about ±2 °C over a volume of about five hundred cubic centimeters. The use of multiple frequencies also enables a clinician to maintain a therapeutically effective temperature within targeted tissue by continuing the application of ultrasound waves of one frequency while ultrasound waves of a second frequency are turned off in order to obtain measurements of the amount and/or rate of ultrasonic energy being delivered. The use of different frequencies also allows a clinician to alter exposure parameters to account for differences in the size and absorptive properties of both targeted and surrounding tissue. The presence of subcutaneous fat proximate to targeted tissue may reduce the absorption of ultrasound and thus may complicate achievement of therapeutic temperature. The use of multiple ultrasound frequencies can minimize the effects of anatomical tissue interference.

When two or more frequencies of ultrasound waves are used in the methods described herein, the difference in frequencies is preferably at least about 0.5 MHz, more preferably at least about 0.75 MHz, and even more preferably at least about 1.0 MHz. Also, preferably the lowest frequency of ultrasound waves applied according to the methods described herein is about 0.6 MHz, more preferably at least about 0.7 Hz, even more preferably at least about 0.8 MHz and still more preferably at least about 1.0 MHz. Preferably, the highest frequency of ultrasound waves applied according to the methods described herein is about 8 MHz, more preferably about 7 MHz, even more preferably about 6 MHz, still more preferably about 5 MHz. In certain highly preferred embodiments, the highest frequency of ultrasound waves applied is about 5 MHz. Thus, for example, two frequencies of ultrasound waves, of which the lowest is about 1.0 MHz and the highest is about 2.25 MHz may be applied. In another example, two frequencies of ultrasound waves, of which the lowest is about 1.5 MHz and the highest is about 3.5 MHz may be applied. Optionally, a ultrasound waves of a third frequency, such as about 2.25 MHz may be used in addition to a lower frequency and a higher frequency. The practical upper limit of useful ultrasound frequencies is determined by the absorption of higher frequencies by tissue, i.e., higher frequencies may be absorbed by surrounding tissue, resulting in little or no ultrasound energy reaching targeted tissue. Generally, it is desirable that the ultrasound frequency be 25 MHz or lower. These exemplary frequencies are provided for illustrative purposes only, as the person skilled in the art will be able to determine and apply a preferred combination of ultrasound frequencies for a particular therapy. Ultrasound waves can be applied to tissue using methods known to those skilled in the art. For example, invasive hyperthermia devices such as implanted transducers and catheters can be used. However, non-invasive techniques for applying ultrasound waves are generally preferred from the standpoint of patient comfort and ease of application. According to the methods described herein, non-invasive methods for administering ultrasound waves are highly preferred. Non-invasive methods for applying ultrasound waves to tissue include the use of an ultrasound transducer immersed in a fluid into which a patient's body, or a portion of a patient's body that encompasses targeted tissue, is also immersed. One apparatus that utilizes such a transducer is described in U.S. Patent No. 4,936,303, the disclosure of which is hereby incorporated herein by reference in its entirety.

Preferred devices for providing ultrasound-generated hyperthermic treatment, include a means for generating unfocused ultrasound waves. Such means are known to those skilled in the art and include, for example, transducers, RF power amplifiers, directional couplers, signal generators, white noise generators and acoustic reflectors, acoustic hydrophones, high- gain frequency selective amplifiers and transient recorders. Also, the devices include a means for determining the efficiency of the transducer and a means for performing dosimetry. Such means are known to those skilled in the art and include, for example, an acoustic force balance, a calibrated hydrophone, and high-absorbing phantom with embedded thermocouple.

Preferably, a device for providing ultrasound-generated hyperthermic treatment includes a means for obtaining temperature data from targeted and/or surrounding tissue in situ. "In situ" means the tissue that is to be treated, in position and prepared for the treatment. The means for obtaining data may include conventional imaging devices, such as MRI scanners. The device also preferably includes minimally invasive thermal probes and a means for inserting and removing such probes. The construction of thermal probes is known to those skilled in the art, and suitable thermal probes include, for example, miniature thermistors and fine-wire thermocouples. In preferred embodiments, the methods and devices disclosed herein incorporate a computer-based controller that can receive data, such as imaging data obtained by ultrasound, computer aided tomography (CT), or magnetic resonance imaging (MRI). Based on the data received, as well as other information such as absorption properties of the targeted and surrounding tissue, ambient temperature, location and distribution of blood vessels in the tissue, flow properties of blood within the blood vessels, the perfusion properties of the blood, heat transfer properties of tissue, density of targeted and surrounding tissue, and sound velocity through the tissue, the controller can determine the appropriate frequencies and exposure times of ultrasound waves to be delivered to the targeted tissue. Preferably, the device includes a computer that can create a three-dimensional model of the targeted and surrounding tissue, prior to, during, and following treatment. The amount of ultrasound energy delivered to the targeted tissue, referred to herein as the "integral dose", and the time at which such energy is delivered to the tissue, referred to as the "integral dose rate", can be controlled based on the properties of the tissue and the desired temperature profile. The desired temperature profile can be determined and input by a clinician, and the computer can control the administration of ultrasound waves to achieve the desired temperature profile. In general, for a desired temperature profile, the actual exposure (dose rate and integral dose) varies depending upon the size and properties of the targeted and surrounding tissue. A central processing unit allows manipulation of the data obtained, and preferably can create a simulated model of the targeted and surrounding tissue including, for example, thermal profiles, density profiles, and dimensions of tissue and blood vessels therein. In addition, it is preferred that the central processing unit can determine from such data the preferred and optimal levels and duration of ultrasound waves to be delivered to the targeted tissue. Thus the duration as well as the associated temperatures maintained can be monitored. This can be advantageous to ensure a particular regimen or perhaps to vary the regimen in an adaptive manner as the treatment progresses. Initially, maintaining and monitoring for particular time and temperature profiles is helpful to permit correlation of treatment conditions and therapeutic results.

Optionally, a device may include one or more pairs of inlet and outlet ports. Such inlet and outlet ports allow the removal of fluid from the exposure tank and/or bag, either temporarily for alteration, or permanently for replacement. Such alteration may include, for example, heating, cooling, or degassing. Degassing of the fluid following removal eliminates the need to apply vacuum directly to the exposure tank.

The foregoing includes exemplary applications of the methods and devices within the scope of the present invention. A number of additional applications and variations also are possible, within the scope of the invention as defined in the appended claims.

Claims

What is claimed is:

1. A method for treating cancer in the lung of a patient, comprising inducing in said lung regional hyperthermia by applying unfocused ultrasound waves to said tissue.

2. A method of claim 1 , further comprising applying to said tissue high-energy radiation.

3. A method of claim 2, wherein said ultrasound waves and said high-energy radiation are applied simultaneously.

4. A method of claim 2, wherein said ultrasound waves and said high-energy radiation are applied sequentially.

5. A method of claim 4, wherein said diffuse ultrasound waves and radiation are applied according to a treatment schedule in which radiation is administered for from about 1 minute to about two minutes, and after a delay of at least about 30 minutes, diffuse ultrasound is applied for at least about ten minutes.

6. A method of claim 5, wherein said radiation is administered for 1.5 minute, said delay is about 30 minutes, and said diffuse ultrasound is applied such that the temperature of the diseased tissue is maintained at 42 °C or higher for at least about 10 minutes.

7. A method of claim 6 wherein said temperature of the diseased tissue is maintained within the range of about 42 °C to about 46 °C for at least about 10 minutes.

8. A method of claim 5 wherein at least one of said administration of said radiation for 1.5 minute and said application of diffuse ultrasound such that the temperature of the diseased tissue is maintained at 42 °C or higher is repeated.

9. A method of claim 5 wherein said treatment schedule is repeated within not less than 3 days.

10. A method of claim 9 wherein said treatment schedule is repeated within not less than one week.

11. A method of claim 1 , further comprising administering to said patient one or more pharmacological agents.

12. A method of claim 1 , wherein said ultrasound waves have a frequency from about 0.6 MHz to about 8 MHz .

13. A method of claim 1 wherein said patient is a human.

14. A method of claim 1 , wherein said application of ultrasound waves is computer controlled.

15. A method of claim 14, wherein said computer controlling comprises obtaining data from said tissue, processing said data, and controlling at least one of the duration and frequency of ultrasound waves applied to said tissue.

16. A method for transplanting tissue from a donor to a recipient, comprising: providing a donor having an initial body temperature; inducing hyperthermia in said donor using diffuse field ultrasound, so that the body temperature of said donor reaches an elevated temperature that is above said initial temperature; maintaining the body temperature of said donor for at least about 20 minutes; allowing the body temperature of said donor to return substantially to said initial body temperature by resting said donor; removing said tissue from said donor; and surgically implanting said tissue into said recipient.

17. The method of claim 16 wherein said tissue is lung tissue.

18. The method of claim 16 wherein said elevated temperature is maintained for at least about 20 minutes.

19. The method of claim 16 wherein said elevated temperature is maintained for at least about 45 minutes.

20. The method of claim 16 wherein said elevated temperature is at least about

43 °C.

21. The method of claim 16 wherein said donor is rested for at least about 6 hours.

22. The method of claim 16 wherein said donor is rested for about 12 hours.

23. A method for treating a wound, comprising inducing hyperthermia in said would by applying unfocused ultrasound waves to said wound.

24. A method of claim 23 wherein said temperature of the wound is maintained within the range of about 42 °C to about 46 °C for at least about 10 minutes.

25. A method for administering hyperthermic treatment to tissue in a patient, comprising: pretreating said tissue using DFHT to induce thermal tolerance in said tissue, and subsequently hyperthermically treating said tissue while said tissue maintains said thermal tolerance.

26. A method of claim 25, wherein said subsequent treatment comprises SFHT.